Energy transfer machine

ABSTRACT

An energy transfer machine is disclosed including a casing enclosing a stator ring, the casing and ring conjointly defining a smooth wall, annular fluid passage extending about the axis of rotation between inlet and outlet passages formed in the casing. A rotor within the casing includes a blade cascade projecting in cantilever fashion into the annular fluid passage, each blade having leading and trailing edges extending generally parallel with the axis of rotation of the machine, the edge nearer the axis of rotation being longer than the edge further from the axis. The geometries and relative positions of the blades and annular fluid passage are such that the radial distance from the axis of rotation of the centroid of the meridional cross-section of the annular fluid passage is larger than the radial distance of at least the major portion of the edge nearer the rotational axis and smaller than the radial distance from the axis of rotation of at least the major portion of the edge further from the rotational axis. Machines according to the invention are also characterized by constructional features which minimize the number of castings required and thereby greatly simplify the fabrication and structure to minimize cost.

United States Patent [191 Egli et al.

[ Jan. 1,1974

[ ENERGY TRANSFER MACHINE [75] Inventorsz Hans Egli, Santa Monica;Fredrick E. Burdette; James H. Nancarrow, both of Torrance, all ofCalif.

[73] Assignee: The Garrett Corporation, Los

Angeles, Calif.

[22] Filed: Aug. 9, 1971 [21] Appl. No.: 169,997

[52] US. Cl. 415/53 T, 415/83 [51] Int. Cl.. F04d 5/00 [58] Field ofSearch 415/52, 53, 53 T,

[5 6] References Cited UNITED STATES PATENTS 745,410 12/1903 Zahikjanz415/56 911,577 2/1909 Dake 415/56 953,013 3/1910 Goldsborough.... 415/563,292,899 12/1966 Egli r 415/5 3,296,972 1/1967 Arkless et a1. 415/53FOREIGN PATENTS OR APPLICATIONS 128,026 /1945 Australia 415/53 T PrimaryExaminerC. .1. Husar Att0rney-Robert H. Fraser et al.

[57 ABSTRACT An energy transfer machine is disclosed including a casingenclosing a stator ring, the casing and ring conjointly defining asmooth wall, annular fluid passage extending about the axis of rotationbetween inlet and outlet passages formed in the casing. A rotor withinthe casing includes a blade cascade projecting in can tilever fashioninto the annular fluid passage, each blade having leading and trailingedges extending generally parallel with the axis of rotation of themachine, the edge nearer the axis of rotation being longer than the edgefurther from the axis. The geometries and relative positions of theblades and annular fluid passage are such that the radial distance fromthe axis of rotation of the centroid of the meridional crosssection ofthe annular fluid passage is larger than the radial distance of at leastthe major portion of the edge nearer the rotational axis and smallerthan the radial distance from the axis of rotation of at least the majorportion of the edge further from the rotational axis.

Machines according to the invention are also characterized byconstructional features which minimize the number of castings requiredand thereby greatly simplify the fabrication and structure to minimizecost.

19 Claims, 19 Drawing Figures PATENIEUJAN 1mm 3.782.850

sum 1 or 8 I NVENTORS EDRICK E. BURDETTE MES H. MARROW nznsm. MDiosucrl, A T TORNE YS PATENTEU H574 1782-850 v snmaurs Q N l 2 IL.

INVENTORS HANS EGLI FREDRICK E.BURDETTE, JAMES H. NANCARROW FQASER ANDBasu m A T TO RN E YS PATENTEUJIW 1W4 3.782.850

' sum 3 or a FIG FIG.4

INVENTORS HANS EGLI FREDRICK E. BURDETTE JAMES H. NANCARROW FRASER Am)ZOGUCKI) ATTORNEYS- PAIENTEW 175m 3.782.850

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ATTORNEYS- Fla-7;

PAIEMEW 11am sum 5 nr 8 INVENTORS HANS EM! FREDRICK E. BURDETTE JAMES H.NANCARROW FPASFR AND 3060mm ATTORNEYS PATENTEDJ-W W4 3.782.850

sum 5 or 3 IN VENTORS HANS EGLI BY FREDRICK E. BURDETTE JAMES H.NAucARRow FzqsEK fWD Eosu kl,

A TTORNEYS PATENT-5mm 115M,

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A TTORNEYS ENERGY TRANSFER MACHINE BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates generally to turbomachines andmore particularly to turbomachines in which the fluid is constrained topass at least twice through the blades of a single rotor.

2. Description of the Prior Art The prior art includes reentry machinesutilizing a single rotor to gain multi-stage performance. These machinesare designed to deliver a high specific work output, that is, a highwork output per unit weight of working fluid. After there has been apartial transfer of energy between the working fluid and the rotor, thefluid is returned to the rotor blades via a return duct or stator vanesfor readmission to the blades and another energy transfer process takesplace. This mode of operation can be continued so that multi-stageperformance is approached with only one rotor. However, reentry machineshave a number of disadvantages including the presence of interstageleakage and the restriction of the flow to a specific, single path ofthe return ducts or stator guide vanes for all load conditions whichpermanently fixes the number of passes made by the fluid through theblades.

In other apparatus of the prior art, the fluid moves in and out of therotor blade passages in a generally uncontrolled and disorderly fashiondue to lack of stator guidance. Because of the disorderliness of theflow, these machines are very inefficient and the net fluid flow throughthe machine ceases at a relatively low limiting value of back pressure.

US. Pat. No. 3,292,899, issued Dec. 20, 1966 to Hans Egli, one of theinventors of the present invention, discloses a multi-pass energytransfer machine representing a major improvement over the describedprior art. Machines according to the referenced patent have specificdiameter and specific speed characteristics falling between that ofconventional turbomachines and conventional rotary, positivedisplacement machines and overlapping considerably into the lattercategory. A further advantage of machines of the cited patent is thatthey will produce, for a given tip speed, a much higher head thanconventional turbomachines, the term head being defined as the energytransfer per pound of fluid.

The fluid energy transfer machine according to one embodiment of thereferenced patent includes a casing having inlet and outlet openings anda plurality of blades arranged in cascade fashion on a rotor formovement in succession past the inlet and outlet openings. The housinghas a smooth interior wall devoid of stator vanes and is so configuredthat the fluid in passing from the inlet opening to the outlet openingis constrained by the walls of the casing to flow in a generallyhelicoidal pattern about a stator ring and through the blade cascade anumber of times. The geometry of the fluid path is primarily dictated bythe shapes of the casing and stator ring, the manner in which the fluidis introduced into the housing (as determined by the shape andorientation of the inlet passage leading to the inlet opening) and thecircumferential pressure gradient which, in turn, depends on the backpressure applied to the machine. Thus, the pitch of the helicoidal flowpath at any specific meridional section of the machine and the totalnumber of times that the fluid passes through the blade cascade arefunctions of back pressure. In order to obtain a practical level ofenergy transfer, the fluid should pass at least twice through thecascade. ln the case of a compressor, for example, for any fluid(whether compressible or incompressible), if the back pressure isincreased while a given rotor speed is maintained, then the number ofpasses of the fluid through the blade cascade increases. The fluid flowpattern is orderly and remains so even though the back pressure isincreased to relatively high levels.

In the prior art machines discussed above, comparatively littleattention is paid, from a fluid dynamics standpoint, to the shaping ofthe rotor blades and their position in the flow passage. This is alsotrue of the block seal separating the inlet and outlet openings. Thus,the overall efficiency of the machine is not optimized. The influence onthe performance of the machine of the geometrical configurations andpositions of the blades and block seal has not been adequatelyappreciated in the prior art.

SUMMARY OF THE INVENTION Broadly, the present invention comprises animprovement of the turbomachine disclosed in US. Pat. No. 3,292,899,referenced above, and among its primary objects are the enhancement ofthe performance and the structural simplification of that type ofmachine.

' According to one specific, exemplary form of the invention, there isprovided a casing defining an interior, smooth-walled toroidal spacepositioned generally concentric of a central axis of rotation and havingsubstantially circular meridional cross-sections. Inlet and outletpassages formed integrally with the casing communicate with the interiorof the casing through inlet and outlet opening situated in closeproximityto one another circumferentially.

The casing encloses a stator ring; of generally circular meridionalcross-section. The ring is positioned concentric of the rotational axisand is spaced from the interior wall surface of the casing to define agenerally annular fluid passage extending circumferentially about theaxis of rotation. The stator ring is disposed relative to the casingsuch that the meridional crosssection of the ring is eccentric withrespect to the meridional cross-section of the toroidal space defined bythe casing, the ring being situated somewhat closer to the outerextremity of the toroidal space with respect to the axis of rotation.According to one embodiment, the stator ring is supported at a pluralityof circumferentially spaced points by axially extending studs at tachedto the casing.

The inlet and outlet openings are separated by a block seal formedintegral with the stator ring and having side surfaces coinciding withmeridional planes.

The block seal is recessed to form a notch blending smoothly with theoutlet passage to minimize losses and disturbances and to permit passageof the blade cascade.

The inlet passage is shaped and. positioned to direct the fluid into theannular fluid passage so that a helicoidal motion is initiated and theoutlet is configured to receive the discharging fluid with minimallosses. In the exemplary form of the invention under consideration, theinlet passage is positioned to direct the fluid generally alongmeridional planes so that at the predominate operating condition, theabsolute velocity vectors of the fluid approach the blades atapproximately 90 with respect to the direction of blade rotationalvelocity. The exhaust passage is oriented approximately in alignmentwith the absolute velocity vector of the exiting flow.

The casing also encloses a rotor having a blade cascade in close runningclearance with the stator ring and extending in cantilever fashion fromthe rotor approximately parallel with the axis of rotation. The bladesare cambered, aerodynamic sections with chord lines oriented at apredetermined stagger angle. The fluid flows in the above-mentionedgenerally helicoidal path about the stator ring and is impelled (in thecase of a pump, blower or compressor) during each pass of the fluidthrough the blade cascade. In this fashion, the inlet and outletpassages introduce and receive the fluid from opposite sides of thecascade.

Each blade has a leading edge and a trailing edge extending generallyparallel with the axis of rotation of the machine. According to anaspect of the invention, the edge nearer the axis of rotation is longerthan the edge further from the axis of rotation. Thus, in the case of anoutflow machine in which the fluid flows away from the axis of rotationduring its passage through the blades, the leading edge of the blade islonger than the trailing edge. The reverse is true for an inflowmachine.

According to another significant aspect of the invention, the geometriesand relative positions of the blades and annular fluid passage are suchthat the radial distance from the axis of rotation of the centroid ofthe meridional cross-section of the annular passage is larger than theradial distance from the axis of at least the major portion of the bladeedge closer to the axis and smaller than the radial distance from theaxis of at least the major portion of the edge further from the axis.This geometry and relative positioning provides a way to assure that theangle of incidence, that is, the angle at which the relative velocityvector of the fluid approaches the blade cascade, will remain nearlyconstant over a wide operating range.

According to another aspect of the invention, in order to more closelysatisfy continuity considerations in the case of compressible fluids,the meridional crosssectional area of the annular fluid passage may bedesigned to decrease (in the case of a compressor or blower) toward thepoint of discharge. This may be accomplished by utilizing a stator ringhaving a meridional cross-sectional area which increases from inlet tooutlet, or alternatively, a casing having an interior wall whosemeridional cross-sectional area decreases be tween inlet and outlet, ora combination of such geometries.

The invention provides a broad operating range over which highefficiencies are obtained, and the relatively low operating speed ofmachines according to the invention permits the use, for manyapplications, of practical drive systems in contrast to conventionaltypes of turbomachines which require rotational speeds too high for suchdrives.

By way of example, the machine of the invention may be designed as anair pump for use in the emission control systems of automobiles. Suchpumps introduce pressurized, secondary air into the exhaust stream toprovide additional oxygen to insure complete combustion of the exhaustproducts. Apparatus according to the invention meets the cost, minimumbulk, simplicity,

and functional and operational air requirements of such systems.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, advantages and featuresof the invention will become apparent by reference to the followingdetailed description in conjunction with the accompanying drawings, inwhich:

FIG. 1 is an exploded, prespective view of an energy transfer machine,designed for operation as an air pump, in accordance with the invention;

FIG. 2 is a front elevation view of the machine of FIG. 1;

FIG. 3 is a side elevation view, partly in section. of the machine ofFIG. 1, the section being taken along the broken plane 3-3 in FIG. 2;

FIG. 4 is a rear view of the macnine of FIG. 1 with certain portions ofthe casing omitted for clarity and showing the path of a typical fluidparticle;

FIG. 5 is a front view of a portion of the rotor of the machine of FIG.1 showing details of the blade cascade;

FIG. 6 is a representation of a straight blade cascade showing certain,pertinent geometric interrelationships;

FIG. 7 is a somewhat schematic, meridional crosssection view of aportion of a machine according to the invention to illustrate certaingeometric relationships for a first, exemplary blade configuration;

FIG. 8 is a meridional cross-section view similar to that of FIG. 7showing the same geometric relationships for a second, exemplary bladeconfiguration;

FIG. 9 is a rear view of an alternative embodiment of the energytransfer machine of the invention, designed for use as an air pump, withcertain portions of the machine omitted for clarity;

FIG. 10 is a cross-section view of a portion of the apparatus of FIG. 9as seen along the plane 10-10;

FIG. 11 is a cross-section view of a portion of the apparatus of FIG. 9as seen along the plane 11-11;

FIG. 12 is a rear view of another alternative embodiment of the energytransfer machine of the invention, designed for operation as an airpump, with certain portions of the machine omitted for clarity;

FIG. 13 is a crosssection view of a portion of the apparatus of FIG. 1as seen along the plane 13-13;

FIG. 14 is a front elevation view of an energy transfer machineaccording to still another embodiment of the invention;

FIG. 15 is a rear elevation view of the machine of FIG. 14 with certainportions thereof omitted for clary;

FIG. 16 is a cross-section view of a portion of the machine of FIG. 14taken along the plane 16-16 in FIG. 15;

FIG. 17 is a side elevation view in cross-section of the machine of FIG.14 taken along the broken plane 1717 in FIG. 15;

FIG. 18 is a top view of a portion of the machine of FIG. 14 showingdetails of the block seal; and,

FIG. 19 is a block diagram of an internal combustion engine andassociated emission control system having a secondary air pumpconstructed pursuant to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Although it will beapparent to those skilled in the art that machines according to thepresent invention can be constructed for operation as pumps, blowers,compressors, turbines, and so forth, utilizing either gas or liquid asthe working fluid medium, for purposes of illustration the drawings andensuing description are directed to an embodiment of the invention whichhas application as an air pump and is particularly useful as a source ofpressurized secondary air in automobile emission control system.

Turning now to FIGS. l-5 of the drawings, there is shown a machineexemplifying the present invention and including generally a casing anda rotor 12 both concentric of a central axis of rotation 14.

The casing 10 is composite, split structure consisting basically of afront casing portion 16 and a rear casing portion 18 joined along aninterface extending generally transverse of the axis 14. The frontcasing portion 16 defines an axially extending cylindrical bore 20enclosing a shaft 22 supported by a pair of ball bearings 24. The rotor12 is attached to the rear extremity of the shaft 22 for rotation aboutthe axis 14. The front casing portion 16 also includes a radiallyoriented inlet passage 26 shaped and positioned symmetrically about ameridional plane 28. The inlet passage 26 communicates with the casinginterior through an inlet opening 29. The rear casing portion 18includes an outlet passage 30 and associated outlet opening 31. Thepassage 30 is oriented so as to be in approximate alignment with theabsolute velocity vectors of the fluid approaching the outlet opening31.

The casing 10 also encloses an annular, intermediate casing portion 32concentric of the axis 14 and positioned between the front and rearcasing portions 16 and 18. The casing portions l6, l8 and 32 havesmooth, arcuate interior surfaces 34, 36 and 38, respectively. Exceptfor an annular opening 40 between the rear portion 18 and theintermediate portion 32, the surfaces 34, 36 and 38 are contiguous andtogether define a smooth-walled, toroidal volume or space whose axis ofrevolution is the axis 14. In meridional cross-section, as shown in FIG.3 for example, the to roidal space has a generally circular appearance,the exact geometry depending upon many parameters including flow rate,rotor speed, pressure ratio, type of fluid, and so forth. For particularapplications, the shape of the toroidal space, in meridionalcross-section, may be varied as required, for example, it may beelongated in a given direction such as in the direction of the axis ofrotation.

Disposed inside the toroidal space defined by the casing 10 is a statorring 42, which, in the example shown, has a generally circularmeridional cross-section. The stator ring 42 is fastened to the frontcasing portion 16 by three studs 44 and is spaced from the interior wallsurfaces 34, 36 and 38 so as to define conjointly with these surfaces anannular fluid passage 46 having a meridional cross-section that isuniform about the axis 14. The ring 42, as best seen in FIGS. 3 and 4,is positioned within the toroidal space so as to be somewhat closer tothe outer extremities of that space. Like the toroidal space in which itis enclosed, the configuration of the meridional cross-section of thering 42 may be varied from that shown in the drawings as required forparticular applications.

The rotor 12 comprises a disk 50 transverse of the axis 14 and havingalong its outer periphery a forwardly projecting rim 52 extendingparallel with the axis l4 into the annular opening 40. Outer and innerrim seals 54 and 56, respectively, on the rear and intermediate casingportions 18 and 32 preserve the circumferential pressure gradient withinthe casing during operation of the machine. Attached to forwardextremity of the rim 52 in cantilever fashion is a cascade of spacedblades 60. As shown in FIGS. 3 and also with reference to FIG. 7, eachblade 60 has an inner edge 62, an outer edge 64, a base 66 and a tip 68.In the particular example shown, the edges 62 and 64 are approximatelyparallel with the axis 14 but it is to be noted that the blades are notlimited to that specific configuration. The edges 62 and 64 may to someextent be out of parallelism with respect to each other and the axis ll4to achieve specific performance characteristics and/or facilitatemanufacture of the rotor. With respect to the latter in particu lar, theorientation of the blade edges approximately parallel with the axis ofrotation makes possible the use of a simple, two-part die for castingthe rotor as a single piece. To facilitate separation of such a die, theblade edges may be provided with draft, that is, the edges may convergetoward the tip at a small angle.

In the specific example shown, the stator ring 42 has a machined,conical face 74 positioned immediately adjacent the blade tips 68. Thetips 68 have a linear configuration and slope relative to the axis 14 soas to be parallel with the conical face 74 as viewed in any meridionalcross-section (see FIGS. 3, 7 and 8 in par ticular). Thus, a constant,minimum running clearance is maintained along the entire circumferenceof the ring 42 about the axis 14 between the face 74 and the blade tips68. The surface 74 may be other than conical so long as it conforms tothe contour of the blade tips and is separated therefrom by a constant,minimum running clearance.

As shown in FIG. 5, each blade 60 has a cambered, airfoil configurationand is set at a stagger angle dz defined by a typical blade chord lineand a meridional plane 82 tangent-to the trailing edge 64 of the blade.According to one specific example, the stagger angle 4) is approximately12 and there are a total of 72 blades.

From the standpoint of optimizing the performance of the machine, it isdesirable to maintain a constant angle of incidence over a broadoperating range. For purposes of the present invention, the definitionof angle of incidence may be understood by reference to FIG. 6 whichshows a straight cascade of blades 90. The representation in FIG. 6 maybe thought of as a portion of the blade cascade on a rotor of infiniteradius with the plane of the drawing coinciding with a plane normal tothe axis of rotation. Each blade has a leading edge 92 and a camber lineor mean line 94 about which the blade surfaces are constructed. Theangle of incidence, B, is defined as the angle between a line 96 drawntangent to the mean line 94 at the leading edge 92 and the vector Vwhich is the component of the relative velocity of the fluid approachingthe cascade in a plane normal to the axis of rotation.

With reference now to FIGS. 7 and 8, the maintenance of a nearlyconstant angle of incidence over a wide range of operation is achievedpursuant to this invention by positioning the blades so that, as viewedin a typical meridional cross-section, the radial distance from the axisof rotation of the centroid of the meridional crosssection of theannular fluid passage lies in between the radial distances from the axisof rotation of at least the major portions of the inner and outer edgesof the blades. The term annular fluid passage, as used throughout thisapplication, encompasses the entire passage about the stator ringincluding that portion of the passage traversing the blade cascade.

Thus, in FIG. 7, which is an enlargement of a typical meridionalcross-section of the machine shown in FIGS. 1-4, the radial distance, rfrom the axis of rotation 14 of the centroid 98 of the meridionalcrosssection of the annular fluid passage 46 is greater than the radialdistance r from the axis 14 to the inner blade edge 62 and less than theradial distance r from the axis 14 to the outer blade edge 64.

In the embodiment of FIG. 7, the edges 62 and 64 are parallel with theaxis 14 so that the centroid 98 lies between the entire extents of theedges 62 and 64. In contrast, in FIG. 8 there is shown a meridionalcrosssection configuration of a machine including blades 600 each havinginner and outer edges 62a and 64a, respectively, that converge towardthe blade tip so as to be non-parallel with respect to each other andthe axis of rotation 14a. In this case, the radial distance, r of thecentroid 98a of the meridional section of the annular fluid passage 46aintersects the inner blade edge 62a. However, in accordance with theprinciples of the invention, all points along at least a major portion,p, of the length of the inner edge 62a lie at a radial distance r, fromthe axis 14a that is less than the radial distance r Further, in theexample of FIG. 8, the entire length of the outer edge 64a lies outsidethe radial distance r to the centroid 98a.

Another geometric interrelationship forming an aspect of the presentinvention and which aids in achieving high performance and efficiency isthat the inner edges of the blades (such as the edge 62) are longer thanthe outer edges (such as the edge 64). This, of course, is a reflectionof the geometry of the annular fluid passage 46 whose radially outwardportions are narrower than the radially inward portions. Stated anotherway, the blade cascade, in a general sense, separates the wider,radially inward regions of the annular passage 46 from the narrower,radially outward regions. This geometry, in cooperation with thecircumferential pressure gradient, results in a rise of static pressure(in the case of a compressor) as the fluid moves from inlet to outlet.

Separating the inlet and outlet openings 29 and 31 is s block seal 100which, as shown in FIGS. 3 and 4, fills and seals the entire fluidpassage along a short sector, the length of which is at least equal tothe spacing between adjacent blades. The inlet and outlet openings 29and 31 are immediately adjacent the block seal 100 so as to be in closeproximity to one another. The block seal 100 is preferably fabricated asan integral part of the stator ring 42 and in this specific embodimenthas flat side faces 102 and 104 which coincide with meridional planes.The block seal 100 further has an arcuate recess 106 to permit passageof the blade cascade, the forward surface 108 of the recess 106 beingflush with the face 74 on the stator ring. The recess 106 is dimensionedso that a minimum running clearance is provided for passage of the bladecascade.

The block seal 100 also has a U-shaped, angularly oriented notch 110fairing smoothly into the outlet passage 30 to minimize losses.

With reference to FIG. 4 which shows, for a compressor, a typicalstreamline 114, that is, the path of a typical fluid particle, the fluidparticle enters the inlet passage 26 and is directed thereby in agenerally radial direction through the inlet opening 29 and under thestator ring 42. The fluid, following a generally helicoidal path, thenenters the blade cascade at point A nearly perpendicular to the bladerotational direction. The energy level of the fluid is increased as aresult of the work done by the blades on the fluid and this increase inenergy level is seen mostly as an increase in absolute velocity and asmall increase in static pressure. As the fluid leaves the blades atpoint B and circulates about the stator ring to the point C, a furtherpressure increase occurs as a consequence of the diffusing action whichconverts kinetic energy (energy associated with velocity) into staticpressure. This diffusing action is a result of the increasing pressureas the fluid advances circumferentially about the axis 14. The fluid,entering at point C, then passes through a portion of the blade cascadea second time and the process may repeat itself several times before thefluid exits via the outlet passage 30. The fluid, at all times, followsa smooth, orderly, generally helicoidal path about the stator ring 42and in the case of a compressible fluid processed by a machine having anannular fluid passage of constant cross-sectional area, that is, apassage defined by a sur' face of revolution about the rotational axis14, the pitch of the generally helicoidal path 114 decreases as thefluid moves circumferentially about the axis 15 into regions of higherpressure.

The particular embodiment under discussion may be designated as anoutflow machine in which the fluid moves through the blade cascade in adirection away from the axis 14. The inner edges 62 thus function as theleading edges of the blade while the outer edges 64 are the trailingedges. It will be appreciated that it is possible, with obviousmodifications based on the disclosure herein, to reverse the fluid flowdirection so that an inflow pattern is established in which the fluidmoves toward the axis 14 during its traversal of the blade cascade. Inthat case, the outer edge becomes the leading edge and the inner edgefunctions as the trailing edge.

Turning now to FIGS. 9 through 13, there is shown a pair of alternativeembodiments the construction of which is such that the meridionalcross-section area of the fluid passage is gradually decreased betweeninlet and outlet so as to enhance the efficiency of the machine whencompressible fluids, such as air, are processed. In the embodiment ofFIGS. 9-11, the meridional cross-section area of the stator ring isgradually increased between the inlet and outlet ends, the inlet end 122having a relatively small cross-section area and the outlet end 124having a relatively large crosssection area. All of the other geometricconsiderations discussed above are retained in this version for highperformance and high efficiency operation.

In FIGS. 12 and 13, the meridional cross-section area of the interiorwall of the casing 132 is gradually decreased so as to obtain the sameresult as that accomplished with the embodiment of FIGS. 9-11. Themeridional cross-section near the inlet end appears as shown in FIG. 10and FIG. 13 shows a typical section near the outlet. In this embodiment,the stator ring 134 has a uniform meridional cross-section area alongits entire length. It will be obvious that a combination of theconfigurations of FIGS. 9-11 and 12-13 may be used, that is, both themeridional cross-section area of the stator ring may be increased andthe meridional cross-section area of the interior wall of the casing maybe decreased gradually between inlet and outlet.

The above-described geometry and orientation of the blades, theorientation and positions of the inlet and outlet passages relative toeach other and to the block seal, and the small number or partsrequired, all contribute, in comparison to the prior art, to furnish acompact, high performance, simple and low cost fluid energy transfermachine.

Further structural simplifications may be achieved by fabricating theintermediate casing portion, the stator ring and the block seal as aone-piece casting. Such an arrangement, along with certain additionalmodifications, is shown in the embodiment of FIGS. 14-18. Thisembodiment of the invention comprises a casing 140 enclosing a rotor 142mounted on a shaft 144 carried by ball bearings 146 for rotation about acentral axis 148. The rotor has a cascade of blades 149 similar to thosealready described. The casing 140 includes a front portion 150, anintermediate ring-like portion 152 and a rear portion 154 joined to thefront portion 150 about the outer periphery of the machine. The casingportions 150, 152 and 154 and an arcuate surface 156 on the rotor 142together define a smooth-walled, interior wall surface 158 having ashape as described in connection with previously discussed embodiments.

The casing 140 encloses a stator ring 160 defining with the wall surface158 an annular fluid passage 161. The ring 160 includes as an integralpart thereof, a block seal 162 having an outer surface 164 conformingclosely to the configuration of the interior wall surface 158. As shownin FIGS. and 18, a part of the surface 164 comprises the periphery of aflange 166 having spaced, radially oriented portions 168 and 170 havingside surfaces lying in meridional planes. The flange 166 furtherincludes an undulation 172 which functions both to reduce the acousticlevel during operation and to define a notch that blends into the outletpassage 174 to minimize losses. The surface 164 may be grooved along itslength, as indicated in the drawings by the reference numeral 176, oralternatively, may be smooth; in either case, appropriate sealing meansis applied to the surface 164 so that a leak-tight joint is provided andthe stator ring is securely held in place.

The intermediate casing portion 152 is supported by two or more ribs 178projecting inwardly from the stator ring. In this way, the ring 160, theintermediate casing portion 152 and the ribs 178 may all be formed as asingle casting. Alternatively, studs (such as studs 44 in the embodimentof FIGS. l-4) may be usedin place of, or in conjunction with, the ribs178. As a further structural simplification, the inner rim seal(reference numeral 56 in FIG. 3) is replaced by a transverse face seal180 between the rotor and intermediate casing portion extending normalto the axis 148.

The front casing portion 150 defines a circumferential, axiallyextending chamber 184 including an enlarged inlet passage 186communicating with the annular fluid passage 161 through an inletopening 188. The

opening 188 extends a short arcuate distance (for example about 60)about the axis 148 and is positioned immediately adjacent the block seal162. The chamber 184 tapers outwardly toward the rear of the machine andis divided into sections by three longitudinal partitions 190, thechamber sections communicating with each other and the inlet passage 186through openings 192 behind the partitions 190. Fluid is introduced intthe chamber 184 through a centrifugal dirt separator 194, the operationand structure of which are well known in the art, and a series ofarcuate intake ports 196. A web 198, centrally positioned within theintake passage 186 strengthens the front casing portion and assists indirecting the incoming fluid.

The fluid entering the chamber 184 has a relatively high absolutevelocity as represented by the vector V The outwardly taperingconfiguration of the chamber 184 provides a diffusing characteristic sothat the fluid entering the annular fluid passage 161 will have a lowerabsolute velocity, represented by the vector V Thus, one function of thechamber 184 is to minimize losses by making the velocity V required atthe inlet opening 188 compatible with the velocity V, produced by thedirt separator 194. The configuration of the chamber 184 and thepresence of the web 198 serve to direct the fluid approaching the inletopening 188 generally along meridional planes so that the fluid entersthe blades 149 approximately perpendicular to the direction of blademovement, similar to that described in connection with the inlet passage26 of the embodiment of FIGS. 11-4. The passage 174 is oriented in thesame direction as the outlet passage 30 of the above mentionedembodiment.

To illustrate an application of the present invention, FIG. 19 is aschematic representation of an automobile internal combustion engine 210and associated emission control system. The emission control systemshown is typical of the systems currently under consideration forgeneral use by the automotive industry to comply with clean airstandards and includes a thermal reactor 212 connected to exhaustpassages 214, a catalytic converter 216 and a muffler 218. An air pump220, which may be of the type disclosed herein, is di rectly driven bythe engine 210 and supplies secondary air under pressure to the exhaustpassages 214 via a flow controller 222.

What is claimed is:

1. A machine for transferring energy between a fluid medium and a shaftrotatable about an axis, comprising:

a casing having inlet and outlet openings and enclosing a stator ringand defining therewith a vaneless fluid passage extendingcircumferentially about said axis; and

a rotor mounted on said shaft and having blades projecting into saidfluid passage, said blades having inner and outer edges relative to saidaxis, the radial distance from said axis to the centroid of themeridional cross-section of said fluid passage lying between the radialdistances from said axis to at least major portions of said inner andouter edges.

2. A machine, as defined in claim 1, in which said inner edges arelonger than said outer edges.

3. A machine, as defined in claim 1, in which at least one of said innerand outer edges extends parallel with said axis.

4. A machine, as defined in claim 1, in which the casing includes inletand outlet passages communicating with said fluid passage throughsaidinlet and outlet openings, said inlet passage being oriented todirect the fluid so that the absolute velocity thereof approaches theblade cascade approximately perpendicular to the direction of movementof said cascade, said outlet passage being oriented in approximatealignment with the direction of the absolute velocity of the exitingfluid approaching said outlet passage.

5. A machine, as defined in claim 1, in which the fluid moves away fromsaid axis of rotation during its passage through the blade cascade.

6. A machine as defined in claim 1, in which the fluid moves toward saidaxis of rotation during its passage through the blade cascade.

7. A machine for transferring energy between a fluid medium and arotatable shaft, comprising:

a casing having a smooth interior wall surface defining a smooth-walledtoroidal space about a central axis of rotation, said casing includingfluid inlet and outlet openings;

a block seal within said toroidal space separating said inlet and outletopenings;

a stator ring mounted within said toroidal space and defining with saidcasing an annular fluid passage extending circumferentially about saidaxis of rotation, the meridional cross-section of said annular fluidpassage having a centroid; and

a rotor mounted on said shaft for rotation about said axis and includingalong its outer periphery a blade cascade, each blade having an inneredge and an outer edge, said inner edge being positioned closer to saidaxis than said outer edge, at least a major part of said inner edgelying radially inward of said centroid and at least a major part of saidouter edge lying radially outward of said centroid.

8. A machine, as defined in claim 1, in which the projection of eachblade on a meridional plane has a generally trapezoidal configurationand includes a tip, said stator ring including a surface immediatelyadjacent said blade tips and having a configuration corresponding tosaid tips.

9. A machine, as defined in claim 7, in which said inlet and outletopenings are in close angular proximity to one another and said blockseal has side surfaces generally coinciding with meridional planes.

10. A machine, as defined in claim 7, in which said casing includesinlet and outlet passages and said block seal has a portion fairingsmoothly into said outlet passage.

11. A machine, as defined in claim 7, in which the meridionalcross-section of said annular fluid passage varies between said inletand outlet openings to compensate for compressibility of the fluid.

12. In a machine for transferring energy between a fluid medium and ashaft rotatable about an axis, said machine including a casing andstator ring enclosed within said casing, said casing and ring definingan annular fluid passage extending about said axis, inlet and outletpassages in said casing in communication with said fluid passage, arotor mounted on said shaft and carrying a blade cascade extending intosaid fluid passage in close proximity to said stator ring, each blade ofsaid cascade having leading and trailing edges, one of which edges iscloser to the axis than the other, the improvement in which the edgecloser to said axis is longer than the other edge.

13. A machine, as defined in claim 12, in which the centroid of themeridional cross-section of said annular passage lies at a radialdistance from said axis that is between the radial distances from saidaxis to at least major portions of said leading and trailing edges.

14. A machine, as defined in claim 12, in which said edges extendgenerally parallel with said axis of rotation.

15. A machine for transferring energy between a fluid medium and a shaftrotatable about an axis, comprising:

a casing having inlet and outlet openings and enclosing a stator ringand defining therewith a fluid passage extending circumferentially aboutsaid axis; and

a rotor mounted on said shaft and having blades projecting into saidfluid passage, said blades having leading and trailing edges generallyparallel with said axis, one of said edges lying closer to said axisthan the other of said edges, the edge closer to said axis being longerthan said other edge.

16. A machine for transferring energy between a fluid medium and a shaftrotatable about an axis, comprising:

a casing having inlet and outlet openings and enclosing a stator ringand defining therewith a fluid passage extending circumferentially aboutsaid axis; and

a rotor mounted on said shaft and having blades projecting into saidfluid passage, said blades having leading and trailing edges generallyparallel with said axis and in which the radial distance from said axisto the centroid of the meridional cross-section of the fluid passagelies between the radial distances to said leading and trailing edges.

17. A machine for transferring energy between a fluid medium and a shaftrotatable about an axis, comprising:

a casing enclosing a stator ring and defining therewith a fluid passageextending circumferentially about said axis, said casing including aninlet passage and an outlet passage, said passages communicating withsaid fluid passage through inlet and outlet openings; and

a rotor mounted on said shaft and including a blade cascade projectinginto said fluid passage and separated from said stator ring by a closerunning clearance, the blades of said cascade having leading edges andtrailing edges, said inlet passage being oriented to direct the fluidgenerally radially to enter the blade cascade approximatelyperpendicular to the direction of movement of said cascade past saidinlet opening, said outlet passage being oriented in approximatealignment with the direction of the absolute velocity vectors of thefluid exiting from said blade cascade.

18. A machine, as defined in claim 17, in which said inlet and outletopenings are in close circumferential approximation and separated by ablock seal having a notch conforming to the contour of said outletpassage.

19. A machine, as defined in claim 18, in which said block seal has sidesurfaces generally coinciding with meridional planes.

1. A machine for transferring energy between a fluid medium and a shaftrotatable about an axis, comprising: a casing having inlet and outletopenings and enclosing a stator ring and defining therewith a vanelessfluid passage extending circumferentially about said axis; and a rotormounted on said shaft and having blades projecting into said fluidpassage, said blades having inner and outer edges relative to said axis,the radial distance from said axis to the centroid of the meridionalcross-section of said fluid passage lying between the radial distancesfrom said axis to at least major portions of said inner and outer edges.2. A machine, as defined in claim 1, in which said inner edges arelonger than said outer edges.
 3. A machine, as defined in claim 1, inwhich at least one of said inner and outer edges extends parallel withsaid axis.
 4. A machine, as defined in claim 1, in which the casingincludes inlet and outlet passages communicating with said fluid passagethrough said inlet and outlet openings, said inlet passage beingoriented to direct the fluid so that the absolute velocity thereofapproaches the blade cascade approximately perpendicular to thedirection of movement of said cascade, said outlet passage beingoriented in approximate alignment with the direction of the absolutevelocity of the exiting fluid approaching said outlet passage.
 5. Amachine, as defined in claim 1, in which the fluid moves away from saidaxis of rotation during its passage through the blade cascade.
 6. Amachine as defined in claim 1, in which the fluid moves toward said axisof rotation during its passage through the blade cascade.
 7. A machinefor transferring energy between a fluid medium and a rotatable shaft,comprising: a casing having a smooth interior wall surface defining asmooth-walled toroidal space about a central axis of rotation, saidcasing including fluid inlet and outlet openings; a block seal withinsaid toroidal space separating said inlet and outlet openings; a statorring mounted within said toroidal space and defining with said casing anannular fluid passage extending circumferentially about said axis ofrotation, the meridional cross-section of said annular fluid passagehaving a centroid; and a rotor mounted on said shaft for rotation aboutsaid axis and including along its outer periphery a blade cascade, eachblade having an inner edge and an outer edge, said inner edge beingpositioned closer to said axis than said outer edge, at least a majorpart of said inner edge lying radially inward of said centroid and atleast a major part of said outer edge lying radially outward of saidcentroid.
 8. A machine, as defined in claim 1, in which the projectionof each blade on a meridional plane has a generally trapezoidalconfiguration and includes a tip, said stator ring including a surfaceimmediately adjacent said blade tips and having a configurationcorresponding to said tips.
 9. A machine, as defined in claim 7, inwhich said inlet and outlet openings are in close angular proximity toone another and said block seal has side surfaces generally coincidingwith meridional planes.
 10. A machine, as defined in claim 7, in whichsaid casing includes inlet and outlet passages and said block seal has aportion fairing smoothly into said outlet passage.
 11. A machine, asdefined in claim 7, in which the meridional cross-section of saidannular fluid passage varies between said inlet and outlet openings tocompensate for compressibility of the fluid.
 12. In a machine fortransferring energy between a fluid medium and a shaft rotatable aboutan axis, said machine including a casing and stator ring enclosed withinsaid casing, said casing and ring defining an annular fluid passageextending about said axis, inlet and outlet passages in said casing incommunication with said fluid passage, a rotor mounted on said shaft andcarrying a blade cascade extending into said fluid passage in closeproximity to said stator ring, each blade of said cascade having leadingand trailing edges, one of which edges is closer to the axis than theother, the improvement in which the edge closer to said axis is longerthan the other edge.
 13. A machine, as defined in claim 12, in which thecentroid of the meridional cross-section of said annular passage lies ata radial distance from said axis that is between the radial distancesfrom said axis to at least major portions of said leading and trailingedges.
 14. A machine, as defined in claim 12, in which said edges extendgenerally parallel with said axis of rotation.
 15. A machine fortransferring energy between a fluid medium and a shaft rotatable aboutan axis, comprising: a casing having inlet and outlet openings andenclosing a stator ring and defining therewith a fluid passage extendingcircumferentially about said axis; and a rotor mounted on said shaft andhaving blades projecting into said fluid passage, said blades havingleading and trailing edges generally parallel with said axis, one ofsaid edges lying closer to said axis than the other of said edges, theedge closer to said axis being longer than said other edge.
 16. Amachine for transferring energy between a fluid medium and a shaftrotatable about an axis, comprising: a casing having inlet and outletopenings and enclosing a stator ring and defining therewith a fluidpassage extending circumferentially about said axis; and a rotor mountedon said shaft and having blades projecting into said fluid passage, saidblades having leading and trailing edges generally parallel with saidaxis and in which the radial distance from said axis to the centroid ofthe meridional cross-section of the fluid passage lies between theradial distances to said leading and trailing edges.
 17. A machine fortransferring energy between a fluid medium and a shaft rotatable aboutan axis, comprising: a casing enclosing a stator ring and definingtherewith a fluid passage extending circumferentially about said axis,said casing including an inlet passage and an outlet passage, saidpassages communicating with said fluid passage through inlet and outletopenings; and a rotor mounted on said shaft and including a bladecascade projecting into said fluid passage and separated from saidstator ring by a close running clearance, the blades of said cascadehaving leading edges and trailing edges, said inlet passage beingoriented to direct the fluid generally radially to enter the bladecascade approximately perpendicular to the direction of movement of saidcascade past said inlet opening, said outlet passage being oriented inapproximate alignment with the direction of the absolute velocityvectors of the fluid exiting from said blade cascade.
 18. A machine, asdefined in claim 17, in which said inlet and outlet openings are inclose circumferential approximation and separated by a block seal havinga notch conforming to the contour of said outlet passage.
 19. A machine,as defined in claim 18, in which said block seal has side surfacesgenerally coinciding with meridional planes.